1. Field of the Invention
The present invention is directed to a system and a method for inducing and measuring a pupillary response, and in particular, a consensual pupillary response in a human subject. The system includes an induction device structured to generate and expose one eye of the subject to a stimuli. The induction device may also include a stimuli adjustment assembly and/or a stimuli control assembly. The system also comprises a measuring device having a monitoring mechanism, and may also include a recording mechanism, a display mechanism, and/or an analysis mechanism. The method of the present invention includes exposing a primary eye of a subject to at least one stimuli, monitoring a secondary eye of the subject and detecting a consensual pupillary response, and analyzing the detected consensual pupillary response.
2. Description of the Related Art
A variety of devices, systems, and associated methodologies have been developed for use in the diagnosis of vision, and in particular, the vision of human subjects. Some of the devices, systems, and methods which have been developed require the active participation of the subject, wherein the subject must be able to comprehend and respond to various visual stimuli presented to them, while other devices, systems, and methods are based upon involuntary responses of the subject to various other stimuli.
Among the most common type of visual diagnostic tool is the simple eye chart which the subject views from a predetermined distance and identifies the various letters and/or numbers which are typically presented on the chart in a series of rows which successively decrease in size from top to bottom. Of course, diagnosis with this tool requires the active participation of the subject in as much as the subject must comprehend and be able to communicate the identity of the various letters and/or numbers presented on the chart. As such, this diagnostic tool has little or no value for infants, small children, or other persons who are unable to comprehend the procedure or to communicate their response.
A similar type of visual diagnostic tool is utilized to test persons for various types of color perception deficiencies, a condition commonly known as color-blindness. There are three main types of color perception deficiencies, each resulting from the loss or malfunction of one of the three types of cones, L-cones, M-cones, or S-cones, which are the portions of the eye which are sensitive to the various wavelengths of light. More in particular, protanopia is the loss of sensitivity to red, and is caused by the malfunction of the L-cones; deuteranopia is the loss of sensitivity to green, and results from the malfunction of the M-cones; and, tritanopia is the loss of sensitivity to blue resulting from the malfunction of the S-cones.
Color-blindness may either be congenital, or it may be acquired, such as, for example, as a side effect of certain pharmacological compositions. One such composition, Ethambutol, an affordable, easily administered, and effective treatment for mycobacterial infections such as tuberculosis and mycobacterium avium intracellularae, which is a common condition in HIV and AIDS patients, cites a decrease in visual acuity as a known side effect, however, it is also noted that the side effect usually subsides if use is promptly discontinued. As a result of this potential side effect, Ethambutol is not normally provided to infants or small children due to the inability to effectively test them for color-blindness to determine if and when use should be discontinued. As such, infants and small children are typically subjected to alternate treatments which generally are more expensive, difficult to administer, often requiring numerous injections rather than oral administration, like Ethambutol, and which may ultimately be a less effective treatment regimen.
Specifically, the typical visual diagnostic tool utilized to test a subject for color-blindness consists of a number, a letter, or a geometric shape being represented by a series of dots of a first color within a field of dots of a second color. Persons with normal color perception are able to discern the pattern of the letter, number, or geometric shape, however, persons with one or more color perception deficiencies may not be able to detect the number, letter, or geometric shape. It is understood, however, that such a diagnostic tool requires the active participation of the person being tested to identify whether or not they see a number, letter, or geometric shape, and to communicate the identity of the number, letter, or geometric shape to the person conducting the test, and is not an effective tool for the diagnosis of infants or small children.
A variety of other devices have been developed to test for color-blindness, such as matching a test color to a reference color, or actuation of a response device when a color change is detected on an output device. Each of these devices once again requires the active participation of the subject whose vision is being tested and, as such, they may not be effectively utilized on subjects who are unable to comprehend the procedural requirements, or to communicate the appropriate responses, including infants and small children.
As indicated above, various other devices, systems, and methods have been developed to allow diagnosis of various parameters of a person's vision which rely upon involuntary reaction of the subject to one or more stimuli. One such device utilizes an infrared light source directed at one pupil of the subject, the subject being otherwise shielded from exposure to visible light. An infrared camera is directed towards the pupil to record the response of the pupil to one or more intermittent visible light stimuli that are projected onto a screen which is positioned within the subject's line of sight. Based upon the response of the pupil, one can presumably diagnose an abnormality in the subject's retina corresponding to the response to the one or more visible light stimuli. While this device does not require the active participation of the subject, as the response of the pupil to the visible light stimuli is involuntary, the device does require specialized, and potentially expensive, infrared camera equipment to capture the response of the pupil to the visible light stimuli and to display the response on a television monitor.
Another method and apparatus provides for exposing one eye of the subject to a visible stimuli and recording the response of the pupil of that eye to evaluate phasic-type neuronal activity. Such phasic-type neuronal activity may result from changes in the visible stimuli such as a change in color and/or luminance. One eye of the subject is covered, such as with an eye patch, while the other eye is tested. Thus, the stimuli and the recording device must both be trained on the same eye of the subject, thereby allowing for incident visible light or other stimuli to reach the eye being tested, potentially producing errors in the results obtained. This method and device do not provide any means for evaluating tonic-type neuronal activity in a subject.
One other method and apparatus has been developed for determining the parameters of a pupillary response in a subject such as, latency, time of constriction, and speed of constriction, following exposure to a visible light stimuli. This method and apparatus again rely upon the use of infrared irradiation of the subject's eye, and measurement of the amount of infrared radiation reflected from the subject's eye both before and after exposure to a visible light stimuli. While this invention may be utilized to indirectly measure the parameters of the various pupillary responses indicated above, neither the method nor the apparatus are directed towards diagnosis of any specific physical condition which may affect the subject's vision.
As such, it would be beneficial to provide a system and associated methodology to test specific parameters of a person's vision, such as color perception deficiencies, which does not require the active participation of the subject. It would also be helpful to provide a system comprising standard components so as to be cost effective, thereby permitting widespread usage among persons requiring such vision testing. Further, it would be beneficial for such a system and method to permit detection and measurement of a consensual pupillary response in one eye of the subject upon exposure of the other eye to a stimuli, such that the exposed eye may be completely isolated from all incident stimuli, to minimize potential error in the results obtained. Additionally, it would be helpful for such a system and method to employ a stimuli control assembly, so as to assure consistency in the stimuli generated, once again, to minimize potential error in the results obtained.